1. Technical Field
The present invention relates to a voltage control oscillator (VCO) in a phase-locked loop (PLL) circuit.
2. Background Art
In interface receiver circuits of HDMI and S/PDIF, transfer clock frequency ranges tend to increase. A PLL is used to recover a clock from a received signal. In use of a PLL, a voltage control oscillator (VCO) with a wide frequency variable range and low jitter is necessary.
In Patent Literature 6 and Patent Literature 7, a ring oscillator including a single-ended inverter has odd-numbered stages. In Patent Literature 1, the amplitude of a differential output (62) is fixed by clamping transistors (104, 106) in an inverter (48). In Patent Literature 5, a high level of an inverter is set to a reference potential to limit amplitude. The load of a differential inverter in a ring oscillator according to the related art uses a resistance or an on-resistance of a transistor in a non-saturated region.